Sequence information will be sought on the transfer RNA (tRNA) and a possible 5S RNA-equivalent ("3SERNA") of animal cell mitochondria. I shall examine mixed tRNA preparations for the presence of homologues to the "universal" GT psi CG sequences of conventional tRNA (which is absent from animal mitochondrial tRNA), and shall seek to determine the nucleotide sequences of 3SERNA and of purified tRNA species. I shall employ combinations of in vivo labeling and "post-labeling" techniques and conventional oligonucleotide fingerprinting and "ladder" procedures. Cultured mammalian (hamster: BHK-21) and insect (Aedes albopictus) cells will be used as sources of RNA, and comparisons will be made between homologous RNA species from these two sources on the one hand, and between animal mitochondrial tRNA and other, more conventional, tRNA on the other. Properties of mixed tRNA from aedes and hamster mitochondria indicate that animal mitochondrial tRNA constitutes an evolutionary extreme, distinct even from fungal mitochondrial tRNA. We aim to assess the extent to which these properties are reflected in novel primary and secondary structure.